Movement limiting means for blades of aircraft sustaining rotors



INVENTOR.

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April 17, 1956 MOVEMENT LIMITING MEANS FOR BLADES OF AIRCRAFT SUSTAININGROTORS Filed 001;. 6, 1951 April 17, 1956 D. K. JovANovlcH 2,742,098

MOVEMENT LIMITING MEANS FOR BLADES OF AIRCRAFT SUSTAINING ROTORS 5Sheets-Sheet 2 Filed 061;. 5, 1951 INVENTOR.

April 17, 1956 K. JOVANOVICH MOVEMENT LIMITING MEANS FOR BLADES OF'AIRCRAFT SUSTAINING ROTORS Filed Oct. 6, 1951 f 2Q l 6T" g f 56% 27h E l3 Sheets-Sheet 3 INVEN TOR.

This invention relates to rotatable sustaining means rates arent O m foraircraft and relates in particular to means for 1iini't' movement of thesustainthe blade and the extreme downward swinging movement m of therotor blade may be referred to as the droop of the blade. Also, theangle which the lowered or drooped blade makes with the normal plane maybe ieferred'to as the droop angle.v i

1t is an object of the invention `to provide aV novel means for limitingthe `fall of the rotor blades, below the normal plane passing throughthe rotor body, characterized by permitting a greater droop of the rotorblades when they are revolving with the rotor head than normally whenthe blades are stationary. 4 I It is an object of the invention toprovide ameansffo'r varying the permissible blade droop angle regardlesswhether the articulated blades are at rest or rotating around the axisof the rotor body. In the invention, when' the blades are at rest, thedroop angle is the samefor all blades, but 'when the sustaining rotorsare being opeirated during extreme maneuver an increase in the droopangle isrpermitted for the blades While they are passing through aportion'of the circular movement which they have about the axis of therotor body.V It is characteristic of articulated sustaining blades whilethey are in operation to swing below the normal plane on one side oftheir circle of revolutionabout the axis of rotation and to'rise abovethe normal plane on the opposite side of 4such circle of revolution.This is sometimes referred to as a app'ing action of the blades. Theinventionis especially useful 1 rotor such as described in the precedingparagraph lhaving shoulders on the blade structures and means 'ofengageinent between such shoulders for normally limiting' the droopangle when the blades. are at rest, but permitting y an increase in thedroop angle when the blades are rotating, and also to permit a greaterdroop angle at the front than vat the rear of the rotor. p

A further object of the invention is to provide a sustaining rotor ofthis type having projecting levers on the rotor structures which haveshoulders for engagement with the engagement means. L Y g A furtherobject of the invention is to provide in a sustaining rotor, anengagement means rfor lthepurfpose set forth consisting of a ringarranged to shift laterally.

2,742,698 Patented Apr. 17, 1956 ICC Afrther object of the invention isto provide a stop for limiting the lateral shifting movement of the ringwhich constitutes the engagement means, thereby limit* ,ing the maximumdroop angle which may be assumed by any of the r'oto'r blades, this stopbeing arranged in one form f the invention to limit the movement of thering to a greater Yextent in one direction than in other directions.

Further objects of the invention will be brought outin the following'part of the specification, wherein apreferred embodiment of theinvetnion has been described in detail for the purpose of disclosure,withoutlimiting the scopey of the invention set forth in the appendedclaims nor limiting the range of equivalents to which the claims areentitled. y

m Referring ot vthe drawings which are for illustrative purposes only:

Fig'. 1 i's an elevational view showing a helicopter with rotors of myinvention thereon;

Fig. 2 is a plan view, to enlarged scale, of one of the rotor bodies,with portions of blade structures extending therefrom, the outer ends ofthe blades being omitted;

Fig. 3 is` a sectional view taken as indicated on the line 3 3 of Fig.2;

Fig'. V4l i's a fragmentary sectional view taken on line line 6--6 ofFig. 5.

In Fig. `l, I show a helicopter 10 of tandem type having fore and att`sustaining rotors 11. The helicopter 10 is shown standing upon theground and the sustaining rotors 11 thereofare at rest, with the bladestructures 12 sloping downwardly( from the rotor bodies 13 thereof. Theblade structures 12 are in drooping position and all of the bladestructures 12 slope downwardly at a droop angle d with relation to anormal plane a-a passing through a rotor body 13. y

It will be Vperceived that the ends of the blades 14 which form parts ofthe blade structures 12 deiine a hori- V-Z'onta-l plane b-b, when thesustaining rotors 11 are at rest.T My present invention permits movementof the rotor structures 12 at certain times so that the ends of theblades at 'these times may pass below the plane b-b, Aas indicated bythe dotted lines 14 in Fig. l.

,In Figs. 2 and 3, I show the essential details of my present invention,omitting parts which are employed for control of the positions of thewing members, since these controls form no part of the present inventionand` may be formed in a number of dierent ways. The rotor body 13 isfixed on the upper end of an upright shaft 15. The 'shaft 15 is hollowand securing screws 16 for the rotor body 13 are passed therethrough andare threaded into an insert 17.

Each blade structure 12 comprises a blade member 14 and connectingvmeans, 13 for connecting the blade member' A14 to the'rotor-` body 13.The connecting means 18 includes a stub shaft 19, the inner end of whichis con'- nec'te'd b'y means of a pin V20 to the rotor body 13 so that itwill swing up and down, and a sleeve 21 supported by bearings 22 sothatV it may have rotary movement on the 'axis of the stub shaft 19, to`enable pitch `adjustment of the wing member 14. The sleeve 21 isVconnected by means of a pin23, which lies substantially in a Verticalplane, and attachment plates 24 with the inner end 25 of the wing member14. Y 'Y K The blade structures 12 havethereonshoulders 26 and means ofengagement v27 disposed so as to engage the arcanes shoulders 26 andhaving the function of limiting the droop angle d, Fig. l, of the bladestructures 12 when they are at rest, and having the further function ofpermitting an increase in the droop angle d as the sustaining rotor 11revolves during certain maneuvers, for example, during horizontalmovement of the craft in the air either forwardly or laterally, orturning. v

The shoulders 26 are formed on the lower portions of levers 28 whichproject downwardly from the inner ends of the stub shafts 19, theshoulders 26 being positioned substantially vertically below the pins 20so that as the wing structures swing down and up, the shoulders 26 willmove in and out. The engagement means 27 comprises rings 27a and 27hsupported within a flat annular housing 2? mounted concentrically uponthe shaft 15 immediately below the rotor body 13. The housing Z9 hastherein radial slots 3% in which the lower ends of the levers 2S maymove as the blade structures swinf7 up and down. The rings 27a and 27hmay move laterally in all directions within the housing 29, the movementthereof in lateral direction is free or unrestrained within the limitsset by a stop ring 31 disposed within the housing 29 and within therings 27a and 2'7b.

When the sustaining rotor 11 is at rest, as shown in Fig. 3, the bladestructures 12 swing down until the shoulders 26 engage thecircumferential surface of the rings 27a and 2711, and due to thesubstantially equal weight of the blade structure 12 they will bebalanced, with the rings 27a and 27b disposed concentrically of theshaft 15 and equally spaced from the peripheral surface of the stop ring31.

During substantially vertical ascent, descent, and hovering of thehelicopter, the blade structures will swing upwardly from the positionsin which they are shown in full lines in `Fig. l to coning positionssuch as shown by the dotted lines c. At this time the blades 14 aredisposed at substantially equal angles relative to normal planes passingthrough the rotor body 13. However, when the helicopter is in extremelateral maneuver, that is, to say moving forwardly, rearwardly orsidewardly; the virtual axis of the cone will incline from the vertical.Due to different relative air speeds and pitch control of the blades 14,the blades 14- will rise on one side of the center of rotation of thesustaining rotor and will droop on opposite side. At this time theengagement means 27 may shift laterally so that the shoulder 26 of thedrooping wing structure 12 may swing further toward the axis of theshaft 15 than the positions of such shoulders 26 shown in Fig. 3. Thiswilt permit an increase in the droop of the drooping blade so that theouter endV thereof may pass below the plane b-b, Fig. l, as indicated at14'. When the engagement means 27 comes into engagement with the stopring 31 further inward movement of the shoulder 26 will be prevented andtherefore maximum droop of a wing during maneuver is limited by the stopring 31. The engagement means 27 is annular, but is is made up of tworings 27a and 27() so that in the event one of the rings fails, theremaining ring will function as the engagement means to control thedroop of the blade structures under conditions of rest and flight aspreviously described` In the form of the invention shown in Figs. 2 to 4inclusive, the stop ring 31 rotates with the shaft 15, and the outerface thereof is concentric to the axis of rotation of the shaft 15. Inthe form of the invention indicated in Figs. 5 and 6, a stationary,eccentric stop ring 31a is employed and a stationary tube or sleeve s isprovided for the support of the stationary stop ring 31a which issecured to the upper end of the sleeve s by screws 35 and is spaced byan annular bearing 36 from a sleeve 37 which is fixed on the shaft 15.In other respects this form of the invention is essentially as shown anddescribed with relation to Figs. 2 to 4. it includes the shaft 1S, arotor body 13 connected to the upper end of the shaft 15 by screws i6which are threaded into an insert fil L. 17 in the upper end of theshaft 15. The rotor body 13 has horizontal pivot means shown as bolts2i) for supporting the shafts 19 which constitute the inner ends of themeans for connecting the blades 14 of thc sustaining rotor. As shown inFigs. 5 and 6, there is a housing 29 which rotates with the shaft 15 andencloses the stop ring 31a and also the rings 27a and 27k, there beingnotches or slots 30 in the housing 29 to receive the shoulders 26 oflevers 28 which project downwardly from the inner ends of the shafts 19.Although Fig. 5 shows only one of the shafts 19 with its downwardlyprojecting lever 2S and shoulder 26, it will be understood that thenumber of these parts corresponds to the number of blades 1demployed inthe sustaining rotor.

In keeping with the position in which the helicopter has been shown inFig. l, the left-hand side of the structure shown in Figs. 5 and 6 isregarded as being the front. The front portion 31b of the stop ring 31ais of the same radial thickness as the side portions 31C thereof but therear portion 31d of the stop ring Sla is of increased radial thicknessso as to provide a lobe to limit leftward movement of the rings 27a and27]). The lobe or thickened portion 31d of the stop ring 31a remainsfixed in view of the fact that the stop ring 31a is stationary. The ring31a limits the lateral movements of the rings 27a and 27h in such a waythat blade droop cannot exceed a limited angle, for example, 3 at therear of the rotor body; whereas it can attain a larger angle, forexample 10, at the front and two sides. The rotor blades may swing downto the larger angle in the front for high forward speeds and may alsoswing down to this larger angle at the sides during extreme lateralmaneuver, but the blades cannot strike the fuselage of the helicopter.

I claim:

l. In sustaining means for aircraft: a rotor body and means forconnecting it to an aircraft; a plurality of blade structures extendingradially from said rotor body, each of said blade structures comprisinga blade member and means for connecting said blade member to said body,said means enabling up and down swinging movement of said blade member;a lever extending from each of said blade structures; a ring disposedaround the axis of rotation of said rotor body and so as to be engagedby said levers when said blade structures are at rest, said ring therebylimiting the droop angle of said blades when they are at rest; meanssupporting said ring for free limited lateral movement across said axisso that during a ight said blade structures may consecutively swingbelow the positions they are caused to assume by said ring when theblades are at rest; and stop means disposed in the path of travel ofsaid ring so as to limit the lateral movement of said ring and therebylimit the maximum extent to which said blade structure may droop.

2. In sustaining means for aircraft: a rotor body and means forconnecting it to an aircraft; a plurality of blade structures extendingradially from said rotor body, each of said blade structures comprisinga blade member and means for connecting said blade members to said body,said means enabling up and down swinging movement of said blade member;engagement means between said blade structures arranged in a planecrossing the axis of rotation of said rotor body and so as to limit thedroop angle of said blades when the blades are at rest; means supportingsaid engagement means for movement in said plane so as to enable anincrease in the droop angle of one of said blades when another of saidblades is raised during revolution of said body and said blades; andstop means disposed in the path of travel of said engagement means so asto limit the lateral movement of said engagement means in one directionso as to limit the maximum droop of the blades to a different extent ona selected side of the circle of rotation of said blades.

3. In sustaining means for aircraft: a rotor body and means forconnecting it to an aircraft; a plurality of blade structures extendingradially from said rotor body, each means for connecting said blademember to said body,

said means enabling up and down swinging movement of said blade member;a lever extending from each of said blade structures along a linecrossing the axes of said blade structure; a ring disposed in a planecrossing the axis of rotationY of said rotor body and in the path oftravel of the ends of said levers so as to be engaged at angularlyspaced points by the ends of said levers when said blade structures areat rest, said ring thereby limiting the droop angle of said blades whenthey are at rest; means arranged to support said ring for lateralmovement, so that during a flight said blades may consecutively swingbelow the positions they are caused to assume by said ring when theblades are at rest; and a stoparing disposed so as to limit'the lateralmovement of said rst namedring, said stop ring being eccentric to theaxis of rotation of the rotor body so as to limit the movement of saidfirst named ring in one of its directions.

4.v In sustaining means for aircraft: a rotor body and means forconnecting it to an aircraft; a plurality of blade structures extendingradially from said rotor body, each of said blade` structures comprisinga blade member and means for connecting said blade member to said body,said means enabling up and down swinging movement of said blade member;a lever extending from each of said blade structures; a ring disposed ina plane crossing the axis of rotation of said rotor body and in the pathof travel of saidV levers so as to be engaged at angularly spaced pointsby said levers when said blade structures are at rest, said ring therebylimiting the droop angle of said blades when they are at rest; meansarranged to support said ring for lateral movement so that dur ing aflight said blades may consecutively swing below the positions they arecaused to assume by said ring when the blades are at rest; and a stopring disposed so as to limit the lateral movement of said lrst namedring, said stop ring having an enlarged portion at a side thereof foreffecting a restriction of the lateral movement of said ring in aselected direction.

5. In sustaining means for aircraft: a rotor body and means forconnecting it to an aircraft; a plurality of blade structures extendingradially' from said rotor body, each of said blade structures co prisinga blade member and means for connecting said blade member to said body,said means enabling up and down swinging movement of said blade member;a lever extending from each of said blade structures; a ring disposed ina plane crossing the axis of rotation of said rotor body and in the pathof travel of said levers so as to be engaged at angularly spaced pointsby said levers when said bladestructures Yare at rest, said ring therebylimiting the droop angle of said `blades when they are at rest; meansarranged to support said ring for lateral movement so that during aflight said blades may consecutively swing below the positions they arecaused to assume by said ring when the blades are at rest; and a stopring disposed so as to limit the lateral movement of said lirst namedring, said stop ring having an enlarged portion at a side thereof foreffecting a restriction of the lateral movement of said ring in forwarddirection with respect to the movement of said aircraft.

6; In sustaining means for aircraft: a rotor body and means forconnecting it to an aircraft; a plurality of blade structures extendingradially from said rotor body, each 0f said blade structures comprisinga blade member and pivot means for connecting said blade member to saidbody, said pivot means enabling up and down swinging movement of saidblade structure; and droop controlling means between said bladestructures, said droop controlling means comprising levers extendingfrom said blade structures, means bodily shiftable in a plane transverseto the axis of rotation of said rotor body and engaging said levers sothat forces incurred in said blades when they tend to move downwardlywill be transmitted toV said transversely movable means inopposingrelation, and means supporting said bodily shiftable means forfree transverse movement. Y

7. In sustaining means for aircraft: a rotor body and means forconnecting it to an aircraft; a plurality of blade structures extendingradially from said rotor body, each of said blade structures comprisinga blade member and means for connecting said blade member to said body,said means enabling up and down swinging movement` of said blade member;a laterally shiftable means surrounding the axis of rotation of saidrotor body; a lever extending from each of said blade structures, saidlevers being arranged so as to engage angularly spaced points of saidlaterally shiftable means and by engagement with said means-limiting thedroop of said blade structures when they are at rest; and meanssupporting said laterally shiftable means for lateral movement so thatduring flight said blades may consecutively swing below the positionsthey are caused to assume by said ring when the blades are at rest.

References Cited inthe file of this patent UNITED STATES PATENTS

